An "add to wishlings" button
Online store owners should have an easy-to-add button they can put on item pages for customers to "Add this item to my wishlings list". This would allow store owners to add wishlist functionality without having to do any hard work.
Further to this you could have branded wishlings lists for store owners to further integrate wishlings into their site.
Or you could do a button like fb did (so you can like something your browsing) for browsers.